scholarly journals Species Diversity Associated with Foundation Species in Temperate and Tropical Forests

Forests ◽  
2019 ◽  
Vol 10 (2) ◽  
pp. 128 ◽  
Author(s):  
Aaron Ellison ◽  
Hannah Buckley ◽  
Bradley Case ◽  
Dairon Cardenas ◽  
Álvaro Duque ◽  
...  
Keyword(s):  
Tropical Forests ◽  
Beta Diversity ◽  
Spatial Association ◽  
Western Hemisphere ◽  
Foundation Species ◽  
Ecological Communities ◽  
Size Frequency Distribution ◽  
Positive Effects ◽  
Size Frequency ◽  
Species Groups

Foundation species define and structure ecological communities but are difficult to identify before they are declining. Yet, their defining role in ecosystems suggests they should be a high priority for protection and management while they are still common and abundant. We used comparative analyses of six large forest dynamics plots spanning a temperate-to-tropical gradient in the Western Hemisphere to identify statistical “fingerprints” of potential foundation species based on their size-frequency and abundance-diameter distributions, and their spatial association with five measures of diversity of associated woody plant species. Potential foundation species are outliers from the common “reverse-J” size-frequency distribution, and have negative effects on alpha diversity and positive effects on beta diversity at most spatial lags and directions. Potential foundation species also are more likely in temperate forests, but foundational species groups may occur in tropical forests. As foundation species (or species groups) decline, associated landscape-scale (beta) diversity is likely to decline along with them. Preservation of this component of biodiversity may be the most important consequence of protecting foundation species while they are still common.

Effects of Predation and Trophic Conditions on the Reproduction of Tylototriton verrucosus (Caudata: Salamandridae) in Darjeeling

2011 ◽  
Vol 4 (2) ◽  
pp. 163-169 ◽  
Author(s):  
Ritwik Dasgupta
Keyword(s):  
Frequency Distribution ◽  
Primary Productivity ◽  
Egg Size ◽  
Zooplankton Abundance ◽  
Trophic Conditions ◽  
Size Frequency Distribution ◽  
Size Frequency ◽  
High Predation ◽  
Hatchling Size ◽  
Predation Rates

The facts that small hatchlings emerged from small eggs laid under high predation levels prevailing at the lower altitudes of distribution of this species in Darjeeling while larger hatchlings emerged from larger eggs laid under lower levels of predation at higher altitudes, show that predation is not selected for large egg and initial hatchling size in this salamandrid species. Metamorphic size was small under high predation rates because this species relied on crypsis for evading predators. Egg and hatchling size are related inversely to levels of primary productivity and zooplankton abundance in lentic habitats. Hatchling sizes are related positively to egg size and size frequency distribution of zooplankton. Small egg and small hatchling size have been selected for at the lower altitudes of distribution of this salamandrid in Darjeeling because predation rates increased in step with improvement in trophic conditions at the lower altitudes.

SIZE FREQUENCY DISTRIBUTION BIASES IN HORSESHOE CRAB MOLT ASSEMBLAGES: IMPLICATIONS FOR THE FOSSIL RECORD

2016 ◽  
Author(s):  
Shelly J. Wernette ◽  
◽  
Scott Evans ◽  
Christine Hall ◽  
Mary L. Droser ◽  
...  
Keyword(s):  
Frequency Distribution ◽  
Fossil Record ◽  
Horseshoe Crab ◽  
Size Frequency Distribution ◽  
Size Frequency

scholarly journals Linking population size structure, heat stress and bleaching responses in a subtropical endemic coral

Coral Reefs ◽  
2021 ◽  
Author(s):  
Liam Lachs ◽  
Brigitte Sommer ◽  
James Cant ◽  
Jessica M. Hodge ◽  
Hamish A. Malcolm ◽  
...  
Keyword(s):  
Heat Stress ◽  
Size Structure ◽  
Temporal Trends ◽  
Early Recovery ◽  
Size Frequency Distribution ◽  
Frequency Distributions ◽  
Community Organisation ◽  
Size Frequency ◽  
Eastern Australia

AbstractAnthropocene coral reefs are faced with increasingly severe marine heatwaves and mass coral bleaching mortality events. The ensuing demographic changes to coral assemblages can have long-term impacts on reef community organisation. Thus, understanding the dynamics of subtropical scleractinian coral populations is essential to predict their recovery or extinction post-disturbance. Here we present a 10-yr demographic assessment of a subtropical endemic coral, Pocillopora aliciae (Schmidt-Roach et al. in Zootaxa 3626:576–582, 2013) from the Solitary Islands Marine Park, eastern Australia, paired with long-term temperature records. These coral populations are regularly affected by storms, undergo seasonal thermal variability, and are increasingly impacted by severe marine heatwaves. We examined the demographic processes governing the persistence of these populations using inference from size-frequency distributions based on log-transformed planar area measurements of 7196 coral colonies. Specifically, the size-frequency distribution mean, coefficient of variation, skewness, kurtosis, and coral density were applied to describe population dynamics. Generalised Linear Mixed Effects Models were used to determine temporal trends and test demographic responses to heat stress. Temporal variation in size-frequency distributions revealed various population processes, from recruitment pulses and cohort growth, to bleaching impacts and temperature dependencies. Sporadic recruitment pulses likely support population persistence, illustrated in 2010 by strong positively skewed size-frequency distributions and the highest density of juvenile corals measured during the study. Increasing mean colony size over the following 6 yr indicates further cohort growth of these recruits. Severe heat stress in 2016 resulted in mass bleaching mortality and a 51% decline in coral density. Moderate heat stress in the following years was associated with suppressed P. aliciae recruitment and a lack of early recovery, marked by an exponential decrease of juvenile density (i.e. recruitment) with increasing heat stress. Here, population reliance on sporadic recruitment and susceptibility to heat stress underpin the vulnerability of subtropical coral assemblages to climate change.

scholarly journals Blocks Size Frequency Distribution in the Enceladus Tiger Stripes Area: Implications on Their Formative Processes

Universe ◽  
2021 ◽  
Vol 7 (4) ◽  
pp. 82
Author(s):  
Maurizio Pajola ◽  
Alice Lucchetti ◽  
Lara Senter ◽  
Gabriele Cremonese
Keyword(s):  
Frequency Distribution ◽  
Power Law ◽  
Size Frequency Distribution ◽  
Surface Stresses ◽  
Size Frequency ◽  
The One ◽  
Power Law Index ◽  
Comet 67P ◽  
South Polar ◽  
Degree Of Fragmentation

We study the size frequency distribution of the blocks located in the deeply fractured, geologically active Enceladus South Polar Terrain with the aim to suggest their formative mechanisms. Through the Cassini ISS images, we identify ~17,000 blocks with sizes ranging from ~25 m to 366 m, and located at different distances from the Damascus, Baghdad and Cairo Sulci. On all counts and for both Damascus and Baghdad cases, the power-law fitting curve has an index that is similar to the one obtained on the deeply fractured, actively sublimating Hathor cliff on comet 67P/Churyumov-Gerasimenko, where several non-dislodged blocks are observed. This suggests that as for 67P, sublimation and surface stresses favor similar fractures development in the Enceladus icy matrix, hence resulting in comparable block disaggregation. A steeper power-law index for Cairo counts may suggest a higher degree of fragmentation, which could be the result of localized, stronger tectonic disruption of lithospheric ice. Eventually, we show that the smallest blocks identified are located from tens of m to 20–25 km from the Sulci fissures, while the largest blocks are found closer to the tiger stripes. This result supports the ejection hypothesis mechanism as the possible source of blocks.

scholarly journals A New Tool to Account for Crater Obliteration Effects in Crater Size-Frequency Distribution Measurements

2018 ◽  
Vol 5 (6) ◽  
pp. 258-267 ◽  
Author(s):  
Christian Riedel ◽  
Gregory Michael ◽  
Thomas Kneissl ◽  
Csilla Orgel ◽  
Harald Hiesinger ◽  
...  
Keyword(s):  
Frequency Distribution ◽  
Size Frequency Distribution ◽  
Crater Size ◽  
Size Frequency

Organisational Learning Capability of Malaysia SMEs: Examining the Effects of Entrepreneurial Orientation and Human-Capital Development Practices

2008 ◽  
Vol 07 (04) ◽  
pp. 219-230 ◽  
Author(s):  
Kwang Sing Ngui ◽  
Peter Songan ◽  
Kian Sam Hong
Keyword(s):  
Human Capital ◽  
Entrepreneurial Orientation ◽  
Structural Equation ◽  
Organisational Learning ◽  
Western Hemisphere ◽  
Equation Modeling ◽  
Human Capital Development ◽  
Learning Capability ◽  
Positive Effects ◽  
Capital Development

The current study built and empirically tested a model of the relationships between selected organisational variables, Organisational Learning (OL) capability and performance in the context of small- and medium-sized enterprises (SMEs) in Malaysia. Theoretical advances in the OL domain have been based on the experiences of large organisations in the western hemisphere. In response, the study focuses on analysing the OL capability of SMEs in a transitional economy, namely Malaysia. Structural equation modeling was applied to analyse the datasets from 256 manufacturing and services SMEs. Statistical results showed that entrepreneurial orientation and human-capital development practices have direct positive effects on SMEs' OL capability. It was further found that human-capital development practices mediated the relationship between entrepreneurial orientation and OL capability. This implied that while entrepreneurial orientation fosters the need for a strong OL capability, human-capital development practices serve as the mechanisms for developing such capability. Lastly, empirical evidence was provided to support the notion that OL capability enhances the performance of SMEs.

scholarly journals Environmental control of natural gap size distribution in tropical forests

2017 ◽  
Vol 14 (2) ◽  
pp. 353-364 ◽  
Author(s):  
Youven Goulamoussène ◽  
Caroline Bedeau ◽  
Laurent Descroix ◽  
Laurent Linguet ◽  
Bruno Hérault
Keyword(s):  
Size Distribution ◽  
Tropical Forests ◽  
Environmental Control ◽  
Global Changes ◽  
Gap Size ◽  
Methodological Framework ◽  
Power Law Distribution ◽  
Dominant Form ◽  
Size Frequency Distribution ◽  
Unmanaged Forest

Abstract. Natural disturbances are the dominant form of forest regeneration and dynamics in unmanaged tropical forests. Monitoring the size distribution of treefall gaps is important to better understand and predict the carbon budget in response to land use and other global changes. In this study, we model the size frequency distribution of natural canopy gaps with a discrete power law distribution. We use a Bayesian framework to introduce and test, using Monte Carlo Markov chain and Kuo–Mallick algorithms, the effect of local physical environment on gap size distribution. We apply our methodological framework to an original light detecting and ranging dataset in which natural forest gaps were delineated over 30 000 ha of unmanaged forest. We highlight strong links between gap size distribution and environment, primarily hydrological conditions and topography, with large gaps being more frequent on floodplains and in wind-exposed areas. In the future, we plan to apply our methodological framework on a larger scale using satellite data. Additionally, although gap size distribution variation is clearly under environmental control, variation in gap size distribution in time should be tested against climate variability.

scholarly journals DISTRIBUCIÓN DE TALLAS Y CONDICIÓN REPRODUCTIVA DEL CALAMAR GIGANTE Dosidicus gigas (D´ORBIGNY, 1835) EN EL GOLFO DE CALIFORNIA

2010 ◽  
Vol 25 (2) ◽  
pp. 103
Author(s):  
J. I. Velázquez-Abunader ◽  
M. O. Nevárez-Martínez ◽  
A. Hernández-Herrera
Keyword(s):  
Frequency Distribution ◽  
Gulf Of California ◽  
Multinomial Distribution ◽  
Reproductive Status ◽  
Distribution Analysis ◽  
Dosidicus Gigas ◽  
Reproductive Condition ◽  
Size Frequency Distribution ◽  
Jumbo Squid ◽  
Size Frequency

Se analizaron cambios en la distribución de tallas, número de cohortes y condición reproductiva del calamar gigante Dosidicus gigas utilizando muestras provenientes de siete cruceros oceanográficos de investigación, efectuados en la región central del Golfo de California, México de 1997 a 2008. En todas las estaciones se muestrearon hasta 25 ejemplares registrando longitud del manto, sexo y fase de madurez gonádica y cuando la captura lo permitió, se realizó un muestreo masivo de 100 ejemplares a los cuales se les midió la longitud de manto. Se definieron hasta tres grupos modales o cohortes en algunos de los meses estudiados a través de la técnica de distribución multinomial. De acuerdo con las fases de madurez se observó una amplia temporada de reproducción con dos picos importantes a lo largo del año que coincidieron con las posibles fechas de nacimiento estimadas para las tallas promedio por cada cohorte de acuerdo a la ecuación de edad-longitud usada en el presente estudio (abril – agosto y octubre - febrero). Se estimó la talla promedio de primera madurez por sexo a través de modelos logísticos; los machos maduran a tallas más pequeñas que las hembras aunque no se encontraron diferencias significativas entre las tallas promedio de madurez por sexo (P > 0.05). Los resultados apoyan la hipótesis de la existencia de múltiples cohortes de calamar gigante en el Golfo de California, dos periodos de eclosión importantes y el número de cohortes presenta variación interanual. Esto sugiere la necesidad de un monitoreo constante del recurso para un mejor manejo de la pesquería. Size distribution and reproductive condition of the jumbo squid Dosidicus gigas (D´Orbigny, 1835) in the Gulf of California Variations in size frequency distribution, number of cohorts, and reproductive status of the jumbo squid Dosidicus gigas were analyzed in samples from seven research oceanographic cruises in the central region of the Gulf of California, Mexico from 1997 to 2008. In each station we recorded sex, gonadic phase and mantle lenght for up to 25 squids. When possible, mantle length was measured for 100 squids. We defined up to three modal groups or cohorts for several months through a multinomial distribution analysis. According to the reproductive status, squids showed a long breeding season throughout the year with two major peaks that match the birth dates estimated by the age-length chart (April to August and October to February). The size at first maturity was estimated by genders; although males were mature at a smaller size than females, no significant differences between were detected. Our results suggest that size frequency distribution and reproductive condition of jumbo squid support the hypothesis of the presence of multiple cohort in the Gulf of California, two important periods of birth, and the number of cohort’s present variation, suggesting the need for a constant monitoring of the resource for a better management of the fishery.

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